Swainson's Warbler
Limnothlypis swainsonii
Shy and difficult to see in deciduous forest with dense understory, often near water. Plain buffy-brown coloration with rufous crown and dark eyeline. Also note disproportionately large, sharp, pinkish bill and pink legs. Shimmies tail side-to-side as it slowly forages on the forest floor, investigating fallen leaf litter for insects. Fairly restricted breeding range in the southeastern U.S.; winters primarily on the Yucatan peninsula and in the Caribbean. Listen for loud, sweet song, similar to Louisiana Waterthrush but without the complex ending.
识别特征
Swainson's warblers are a small and rather nondescript songbird, though are fairly large for a New World warbler. Adults grow to 12.5–16 cm (4.9–6.3 in) in length and 11–20.5 g (0.39–0.72 oz) in weight. The wingspan averages 23 cm (9.1 in). They are a plain olive-brown above and pale yellow-white below. They have a whitish eyebrow stripe that runs above their eye, and the top of their head is a rusty brown. Unlike most other New World warblers that are mostly dimorphic, there is no difference in appearance between a male or female Swainson's warbler.
分类信息
No subspecies are recognized. There appears to be some divergence between populations from Arkansas and others of the coastal plains. This does fit a pattern one would expect from genetic drift, but there seem to be no geographical or ecological barriers restricting gene flow. Even during the last ice age, when average temperatures, precipitation and sea levels were lower, there seems to have been ample contiguous habitat. Clearly, some factor restricting gene flow is at work, but it is not presently known what it is. It is possible that the subpopulations conform to the different wintering areas.<p>In some migrant birds it is known that the initial direction of the migration is set by fairly simple hereditary mechanisms. Offspring of pairs comprising birds of different subpopulations will, in such species, attempt to migrate into an intermediate direction. Such a course would lead a Swainson's warbler deep into the Caribbean where there are no wintering or even stopover points, and the bird would almost certainly perish. More research such as analyzing bird banding data is needed to determine whether this mechanism applies in Swainson's warbler.
- 学名
- Limnothlypis swainsonii
- 命名信息
- (Audubon, 1834)
- 目
- Passeriformes
- 科
- Parulidae
- 属
- Limnothlypis
分布与栖息地
Swainson's warblers are uncommon, mostly found in flooded swamplands and canebrakes of the south-eastern United States. More rarely, they will also occur in rhododendron thickets in the southern Appalachian Mountains. They are a migratory species, with part of the population migrating southeastwards to the Greater Antilles (where it overwinters in the Blue Mountains of Jamaica for example) and the other southwestwards to the Yucatán Peninsula region in winter.
- 繁殖区
- NA : se USA
- 非繁殖区
- MA and West Indies
- 迁徙
- Complete migrants
行为
Migration pattern: Complete migrants.
保护状况
Population trend: rising.
- 种群趋势
- rising
照片
分布
鸟叫声
其他鸟类
Rusty-crowned Tit-Spinetail
Leptasthenura pileata
Attractive, long-tailed bird found in the high Andes of Peru. Plumage is brown overall with a chestnut crown, speckled throat, and streaked belly. Plumage varies geographically, and birds in southern Peru are much darker below with bolder streaking. Inhabits scrub and woodland with short trees. Vocalizations have a metallic quality; they include a high-pitched trill and a series of sharp chips.
Black-naped Oriole
Oriolus chinensis
Typical yellow and black Old World oriole. Male entirely golden-yellow apart from black wings and tail and a broad black band through the eyes. The tail and wings have yellow tips. The bill is deep pinkish. Female similar to the male but with more yellowish-green upperparts. Juveniles show streaked underparts. Found in a variety of forest habitats, including plantations and gardens; forages in forest canopy.
Arrowhead Piculet
Picumnus minutissimus
Common piculet of coastal forests. Note short-tailed profile, large feet, and cone-shaped bill. Found in mangroves, gardens, abandoned plantations, and disturbed areas. Creeps quietly through vine tangles and bores into dead twigs at lower and middle levels. Similar to Golden-spangled and White-barred Piculets, but Arrowhead has chevron-shaped spots (not barring) on the breast and belly, and is strictly confined to coastal habitats.
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